1. Technical Field
The present disclosure relates to a method for fabricating light emitting semiconductor device and applications thereof, and particularly relates to a wafer level light emitting semiconductor device and applications thereof.
2. Background of the Present Disclosure
Light emitting semiconductor devices having advantages of low power consumption, less heat generation, long life, small size, impact tolerance, high speed, free of mercury and good optical performance have been applied as a light source with steady wavelength in various electronic devices. The brightness and operational life of a light emitting diode (LED) device have been tremendously improved along with the development of the optical technology, and so LED devices may serve as the primary light source of electronic devices in the future.
An LED device with white light is typically made by a LED die encapsulated by a phosphor compound mixed with at least one phosphor, whereby the phosphor is activated by a portion of the blue light emitting from the LED die to derive the blue light into yellow light, and the yellow light is then mixed with the other portion of the blue light to produce white light which in turn emits from the LED device.
Conventionally, the steps for coating the phosphor compound onto the LED die are conducted in the device packaging process. During the packaging process, a die should be mounted onto a substrate prior to the phosphor compound being coated thereon. However, since the phosphor compound is directly blanketed over the LED die, the phosphor mixed in the fluid compound may be precipitated to the periphery of the LED die during the compound coating process. Furthermore, the fluid compound may be aggregated on the lateral side of the LED die, so the resulting LED package may have a horizontal thickness greater than the vertical thickness thereof. Thus the initial blue light provide by the LED die and the yellow light derived from the phosphor cannot be mixed adequately, resulting in the light emitted laterally from the LED package having a color temperature different from light emitted vertically form the LED package. In addition, the brightness of the LED package may be decreased.
To resolve these problems, an advanced method has been applied. FIGS. 1A to 1F illustrate cross-sectional views of a LED packaging process in accordance with a conventional packaging method. First pluralities of LED die units 100 are flipped and mounted on a substrate, such as a silicon substrate 101. A conformal coating process, such as screen painting or a thick film process, is then conducted to form a photoresist layer 103 over the substrate 101 and the LED die units 100, and a plurality of openings 104 are formed in the photoresist layer 103 by a patterning process to expose the LED die units 100. Subsequently, a compound 105 mixed with phosphor is filled into the openings 104. A backing process is then conducted prior to the photoresist layer 103 being peeled. The packaged LED die units are then separated from the substrate 101; and each of the die units 100 is bonded with wires to from a LED device.
However, the mounting steps may affect the accuracy for aligning LED die units 100 mounted on the substrate 101 with the openings 104 formed in the photoresist 104 during the LED device batch manufacturing process. The phosphor compound may not encapsulate the LED die in equilibrium. Thus light provided by the resulting LED device may have an undesired color temperature, and the brightness of the LED device may be decreased. Also, the heat-dispersing efficiency of the LED device may be reduced by the disequilibrium of phosphor compound coated on the LED die.